The metabolic pathways involving the formation or utilization of glucose and fatty acids in mammals are subject to a variety of control processes. One predominant type of control mechanism involves the action of hormones on the rate of production (and possibly the destruction) of cyclic AMP and in turn its action often indirectly through protein kinases on various processes and enzymes. The question is asked : Does this chain of control reactions in mammals represent an evolutionary development in which changes can be detected as one descends the socalled phylogenetic tree. It is proposed to investigate the factors regulating the metabolism of glucose and fatty acids in various marine organisms in an attempt to obtain some insight into this question.